1. Field of the Invention
The present invention relates generally to devices to prevent or hinder tampering with electric watthour meters and, in particular, an indicating device in which removal of the meter from the socket or the cover from the meter is permanently indicated by the breakage of a glass vial containing a dye material.
2. Description of the Prior Art
The use of induction type watthour meters installed in meter sockets at customers' sites is well known in the electric utility metering field. Total electrical energy consumption is indicated on one or more register dials on the watthour meter which are driven by a geared disk which, in turn, is driven by a shunt induction motor. This system continually increments the dial or dials to show total electrical energy use. The dial or dials are read periodically for the purposes of billing by utility companies. Thus, the dial on the electric watthour meter is normally the only check which the utility company has pertaining to the total electric energy consumption by a particular customer. This had led to wide-spread tampering of watthour meters in an effort to reduce the indicated consumption and thereby defraud the utility company through indication of less-than-actual power consumption. The Edison Electric Institute (EEI) estimates that the total United States utility industry loses more than four hundred million dollars annually to meter cheaters. Other estimates by utility experts run as high as two billion dollars annually.
A large share of the meter tampering is done by residential and commercial customers with single phase induction watthour meters. Of the more than twenty-five commonly detected methods of meter tampering, more than two-thirds of these require either removal of the meter from its socket or removal of the cover glass.
One well known method of meter tampering involves removal of the meter from its socket and reinstallation of the meter in an upside down position so that the terminals are reversed and the meter registers are caused to run in reverse, thereby reducing the total indicated power consumption without interruption of the power supply to the user. Other popular methods include delivering a blow to the meter such that the induction drive system is permanently disturbed and the mechanism runs at a slower rate for a given amount of power throughput, and using an external magnet to slow or even stop the operation of the induction disk drive system. In some cases the glass is removed and the dial readings changed or the operation of the mechanism otherwise interfered with to affect the meter reading. In a publication entitled "Meter Tampering Report" published in June 1978 by Texas Electric Cooperatives, Inc. it is estimated that the above overt methods account for about 85% of the total meter tamperings. Other, more subtle, methods account for the remainder.
One clever prior art approach to the problem associated with reinserting the meter upside down is disclosed in U.S. Pat. No. 4,039,943 issued Aug. 2, 1977. If the meter is equipped with a gravity switch which together with an auxiliary magnet cooperates to not only to cause the meter to operate in the forward direction when installed upside down, but also causes it to run at a greater rate than that indicated by the actual power consumed, thereby penalizing the defrauder.
Various other schemes and devices have also been utilized in an attempt to stop the other common methods of defrauding the power company. However, there remains a definite need for a type of device which is low cost, easy to install and prevents most or all of the most common methods of meter cheating.